Make meshes simulate like water?
You can approach it like this:


Make simple fluid sim, low resolution will be enough:


Create a plane and subdivide to get your blocks "resolution", position it very high above the water. Add Shrinkwrap modifier to project it onto the simulation:


Parent a little cube under the plane and set dupli verts:


Render it with plane transparent:


Add an ground plane and make column of little cubes from just 1 little cube (to fill holes in water):


As this is based on a voxel simulation you don't get data how the cubes move inside the volume (or on the surface), they are just stationary. To do that you would have to base it from particles. Thats for another approach, this is super fast to setup and simulate.